Exam

Visual Acuity

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Visual Acuity, Vision Screening, Snellen Chart

  • Precautions
  1. Visual Acuity is THE Vital Sign of the eye
    1. Obtain Visual Acuity on all patients with eye complaints
  • Exam
  • Distance Vision
  1. Vision with each eye individually and together
  2. Appropriate chart (usually 10 foot distance to chart)
    1. Snellen Letters (6 years and older, adults)
    2. Snellen Numbers (Non-english speaking or illiterate)
    3. Tumbling E (Children ages 3 to 5 years)
    4. HOTV (Children ages 3 to 5 years)
    5. Picture Tests (Childen ages 3 to 5 years)
  3. Myopia suggested if Vision improves with pinhole
    1. Vision testing through a small pinhole corrects for Refractive Errors
    2. Consider pinhole for vision testing in a patient who did not bring their glasses to evaluation
  4. If vision less than 20/200, assess best vision with:
    1. Finger Counting (CF) at 1 foot and at 6 inches
    2. Hand Movements (HM)
    3. Light perception (LP)
    4. No light perception (NLP): total blindness
  • Interpretation
  • Normal Vision for children 2.5 to 6 years
  1. Month 30-35: 20/60 (or 6/20) or better
  2. Month 36-47: 20/50 (or 6/15) or better
  3. Month 48-59: 20/40 (or 6/12) or better
  4. Month 60-72: 20/30 (or 6/10) or better
  5. Pan (2009) Opto Vis Sci 86(6): 607-12 [PubMed]
  • Evaluation
  • Indications for referral to eye care specialist
  1. Indications for adults
    1. See Preventive Eye Examination for screening guidelines (e.g. Glaucoma)
    2. Uncorrected vision <20/50 or
    3. One line difference (on Snellen Chart) between eyes
  2. Indications for children
    1. Age 4-5: Either eye worse than 10/20 or 20/40
    2. Age >5: Either eye worse than 10/15 or 20/30
    3. Two line difference between eyes
      1. Example: OD 20/25 and OS 20/40
    4. Reference
      1. (2003) Pediatrics 111:903 [PubMed]
  • Exam
  • Near Vision
  1. Not generally screened
  2. Presbyopia occurs after age 40 years
  1. Performed by Optometry or Ophthalmology
  2. Measures optical error of eyes to prepare lenses